1. Field of the Invention
The present invention relates to a structure of a suction valve of a piston type compressor in which a suction port for sucking refrigerant gas is opened and closed by the suction valve, and the refrigerant gas is sucked into a cylinder bore by the suction valve which is pulled apart from the suction port by a sucking motion of a piston arranged in a cylinder bore.
2. Description of the Related Art
In the case of a piston type compressor disclosed in Japanese Unexamined Patent Publication No. 9-273478, while a suction valve is being moved from a closing position to the maximum open position, at which the degree of opening becomes maximum, vibration of the suction valve is caused, and sucking pulsations are caused by this vibration of the suction valve. These sucking pulsations vibrate an evaporator incorporated into an external refrigerant circuit and generate noise. In Japanese Unexamined Patent Publication No. 2-161182, there is disclosed a suction valve structure for preventing the occurrence of vibration of the suction valve. In this conventional device, two suction ports are arranged for one cylinder bore, one is a primary suction port, and the other is an auxiliary suction port. The primary suction port is opened and closed by a primary suction valve, and the auxiliary suction port is opened and closed by an auxiliary suction valve. When the piston starts its sucking motion, first, the auxiliary suction valve starts moving from a position at which the auxiliary suction port is closed by the auxiliary suction valve to a position at which the auxiliary suction valve comes into contact with an engaging recess so that the maximum degree of opening can be determined. Next, the primary suction valve starts moving from a position at which the primary suction port is closed by the primary suction valve to a position at which the primary suction valve comes into contact with an engaging recess so that the maximum degree of opening can be determined. The auxiliary suction valve is moved to the position at which the maximum degree of opening of the auxiliary valve can be obtained before the primary suction valve is moved to the position at which the maximum degree of opening of the primary valve can be obtained. Since the auxiliary suction valve is integrally formed on the primary valve in an opposite direction, when the auxiliary suction valve comes into contact with the engaging recess, the occurrence of the vibration of the entire suction valve can be suppressed.
However, according to the structure in which the auxiliary suction valve is integrally arranged in the opposite direction on the primary suction valve which is moved in the same manner as that of the auxiliary suction valve, it becomes difficult to set a degree of the easiness of opening the auxiliary and the primary suction valve. Both the auxiliary and the primary suction valve are flexible valves, in which deflection is caused in such a manner that the closer to the forward end portions, the more deflection is caused in the valves.
However, in the above structure, there is a restriction that the length of the auxiliary suction valve arranged on the primary suction valve, that is, the distance from the root of the auxiliary valve to the auxiliary suction port is approximately half of the distance from the primary suction port to the auxiliary suction port. Due to the above restriction, it becomes difficult to easily open the auxiliary suction valve, and further it becomes difficult to ensure the maximum degree of opening of the valve within the limit of elasticity. When it is difficult to open the auxiliary suction valve, it becomes difficult to suppress the occurrence of self-excited vibration.
It is an object of the present invention to provide a structure of a suction valve of a piston type compressor effective for preventing the occurrence of abnormal sounds caused by vibration of the suction valve.
In order to accomplish the above object, the present invention provides a structure of a suction valve of a piston type compressor in which a suction port for sucking refrigerant gas is opened and closed by the suction valve, and the refrigerant gas is sucked into a cylinder bore by the suction valve which is pulled apart from the suction port by a sucking motion of a piston arranged in a cylinder bore, the structure of the suction valve comprising: a plurality of suction ports corresponding to one cylinder bore; a plurality of suction valves corresponding to each suction port, respectively; a plurality of maximum opening degree restricting means for restricting the maximum opening degree of each suction valve when the maximum opening degree restricting means comes into contact with each suction valve, corresponding to each suction valve, respectively; and a plurality of opening performance restricting means for restricting the opening performance of the suction valves to open the suction ports, corresponding to each suction port, respectively, wherein the opening and closing motions of the plurality of suction valves are made independent from each other, and the opening performance of at least one of the plurality of suction valves is enhanced more than the opening performance of at least one of the other suction valves.
In a state in which a rate of flow is low, that is, in a state in which a rotating speed of a compressor is low or alternatively a variable capacity type compressor is operated in a small capacity condition, only a suction valve, the opening performance of which is high, opens a suction port, and the opening performance is set so that this suction valve can be immediately transferred to the maximum opening degree position at which the suction valve comes into contact with the maximum opening degree restricting means. When the opening performance is set as described above, in a suction stroke of the piston in the state in which the rate of flow is low, only the suction valve, the opening performance of which is high, opens the suction port, and this suction valve can be immediately transferred to the maximum opening degree position. The above structure, in which the suction valve, the opening performance of which is high when a rate of flow is low, is immediately transferred to the maximum opening degree position when the sucking motion is started, is effective for suppressing the occurrence of vibration of the suction valve.